Ethereal

As an infinity Nikki player I don’t think the whole game has a set style but more like genres of it let me it explain as you already know in the game you can dress as you want so if you wanted to dress punk then You could ect but if you’re talking about how Nikki the character dresses then I’d say a Lolitaish style she wears a lot of lace a ribbon in the game so I’d go with something similar another thing I personally thought of when it came to Nikki’s outfit was jirai kei but that’s all

The one she's wearing at the first picture kinda looks like. jirai Kei type of style, a japanese fashion subculture.

It reminds me more of girly kei than traditional jirai kei. It could even work as Lolita fashion depending on who’s/what guidelines you’re following